The present invention relates to a method of controlling a seatbelt retractor having a mechanism for retracting a seatbelt with a motor.
A typical seatbelt retractor provided in a vehicle has a function of retracting an excessively withdrawn portion of a seatbelt when a seated occupant pulls out the seatbelt and fastens a tongue to a buckle. To achieve such a function, a conventional seatbelt retractor is provided with a single return spring. When a seatbelt is fastened, a person pulls out the seatbelt against a resilient force of the return spring. When the person attaches a tongue to a buckle and releases the seatbelt, the seatbelt retractor retracts an excess portion of the seatbelt with the return spring until the seatbelt fits the occupant.
As described above, in such a seatbelt retractor, it is necessary to properly retract an excess portion of the seatbelt until the seatbelt fits the occupant. When a seatbelt is not used, it is necessary to securely retract the seatbelt until the seatbelt is properly stored in a housing. When a seatbelt is properly worn by the occupant, the seatbelt must not provide an unnecessary pressure to the occupant, for example, a chest of the occupant.
In the seatbelt retractor with the single return spring, when the spring has a low resilient force to reduce the pressure on the chest of the occupant wearing the seatbelt, the force for retracting (for storing) the seatbelt is also reduced, thereby making it difficult to operate and retract the seatbelt smoothly. In contrast, when the spring has a high resilient force to obtain a sufficient force for retracting the seatbelt, the pressure on the chest of the occupant wearing the seatbelt is increased.
Further, in the conventional seatbelt retractor with the single return spring, the return spring is wound as the seatbelt is withdrawn further, thereby increasing the resilient force of the spring. Accordingly, the retracting force increases as the withdrawn length of the seatbelt increases.
To solve such problems, Japanese Patent Publication (Kokai) No. 2001-225720 has disclosed a method of retracting a seatbelt with a seatbelt retractor having a motor or a combination of a motor and a return spring. Such a seatbelt retractor provided with a mechanism for retracting a seatbelt with a motor has been also disclosed in Japanese Patent Publications (Kokai) No. 11-301407 and No. 11-334533.
In the seatbelt retractors provided with the mechanism for retracting a seatbelt with a motor, the seatbelt is generally retracted when the seatbelt is released from a buckle. Further, it is convenient that the seatbelt is retracted when the occupant gets out of a vehicle. For this end, it is preferable to provide a door switch or the like so that when a signal indicating that a door is opened is received, a seatbelt is retracted.
In general, a door is opened not only when an occupant tries to get out of a vehicle, but also when an occupant tries to enter a vehicle. When an occupant enters a vehicle, a seatbelt is already in a completely retracted state. Accordingly, it is a waste of energy, i.e. battery power, for driving a motor to retract a seatbelt in such a case.
In view of the problems described above, an object of the present invention is to provide a method of controlling a seatbelt retractor to retract a seatbelt only when an occupant tries to get out of a vehicle, thereby providing smooth seatbelt retraction for the occupant and preventing waste of battery power.
Further objects and advantages of the invention will be apparent from the following description of the invention.